Footage showing police officers pinning a Labour MP's researcher to the ground outside the Houses of Parliament - in what the researcher says was an unprovoked attack - has been released for the first time.

The conduct of the Crown Prosecution Service has been called into question after the collapse of criminal proceedings against the Labour researcher. 28 year-old Alex Bryce, who works for the Labour MP Tom Blenkinsop, was arrested on the 28th of June 2011 along with his partner, Iain Feis, outside Parliament. The men were subsequently charged with assaulting and obstructing a police officer, on the basis of claims made by two constables working in Westminster that evening.

The case proceeded to court in December and almost immediately collapsed when CCTV images undermined several key claims by the officers, including that the men had "charged" at the officers. Instead the CCTV footage, handed to HuffPost UK by the researcher, shows Ian Feis walking along Bridge Street, underneath Big Ben, appearing to mind his own business, before being thrown to the wall by one of the officers.

The CCTV then shows the man being pinned down by one police officer, before another officer joins in. According to Alex Bryce, one of the officers had earlier seized his Parliamentary pass having heard one of a group of five people swearing outside the gates of Parliament. This initial altercation was not covered by CCTV, despite being directly outside one of the most important buildings in Britain.

The police then claimed that Bryce's civil partner ran away from police up a busy street, although CCTV footage subsequently showed Ian Feis walking calmly up Bridge Street, with no other pedestrians in sight. Cameras then recorded one of the officers seizing Ian Feis and pinning him to the wall, before bringing him to the ground.

In court the officers were unable to justify why they took this course of action, and why the CCTV was unable to support their version of events.

Alex Bryce then joins his partner in the CCTV images, and is also brought to the ground. At one point in the CCTV footage one of the officers is clearly seen punching Alex Bryce in the face as he remained pinned to the floor.

The district judge presiding over the case is said to have suggested the prosecution abandon the trial. It is unclear why the CPS allowed the trial to go to court when the CCTV images so clearly contradicted statements made by the two officers. The defendants had requested the CPS release to their counsel the CCTV images before the trial. Despite this the first time the defendants were able to view the footage was on the first day of their trial.

Alex Bryce was suspended from his job in Parliament for six months pending the trial and has now complained to the Crown Prosecution Service and the Independent Police Complaints Commission about his treatment. He is due to return to work at the end of January having been cleared. "I feel disillusioned with the whole system, It was a case of guilty until proven innocent," he told HuffPost UK. "In politics mud sticks, I feel I had a good reputation which has been damaged. A lot people have been incredibly supportive but some people haven't.

"The amount of stress that we and our families have been put through is incredible. Our families believed our accounts but they hadn't seen the CCTV footage. When they saw the images there was no cause for anyone to have any doubts about what we'd said."

Describing the police officer as "completely irrrational", Bryce claimed officers had operated outside of the law.

"The guy had a problem, I don't know what the problem was. These two police officers have clearly spent their careers thinking they can just push people around. Parliament made no attempts to see the CCTV footage, my account was never asked for.

"Not only has this been a traumatic experience for us, the spectacular incompetence of both the CPS and the Met demonstrated in this case has cost the tax payer a fortune."

The Speaker of the House of Commons has said it's a matter for the Metropolitan Police because the incident took place outside the Parliamentary estate.

The CPS and Metropolitan police have not responded to HuffPost UK's inquiries or requests for comment.